JPH04198407A - Sintered metal mold and production thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial field] The present invention is applicable to plastic injection molding, aluminum diamond
This invention relates to a metal mold made of iron-based metal powder used in . . . and a method for manufacturing the same.

[Prior Art] A mold used for plastic injection molding or the like is provided with a passage through which water flows in order to control the cooling rate of the molded product.

For example, published patent No. 57-500029 discloses that in molds and their manufacturing methods such as plastic deck injection molding using powder metallurgy, improvements in the metallographic structure of the molds during mold manufacturing, and In order to control the cooling rate of the plastic injection molded product during use, it is disclosed that a metal tube having a melting point higher than the sintering temperature of the metal powder is buried for flowing cold air or cooling water. Moreover, although the tube may react with metal powder or infiltration material during sintering, it is necessary that the reaction does not reach the inside of the duplex after sintering and the tube fulfills its purpose as a cooling passage. The material of the tube is steel, preferably stainless steel.If the purpose is only to control the cooling rate, the purpose can be achieved by burying a duplex with a high melting point.

However, when manufacturing molds by infiltration and sintering, the following problems arise.

[Problem to be solved by the invention]

In the method disclosed in the above publication, firstly, the distance between the upper part of the packed bed where the infiltrant is placed and the lower part of the packed bed used as the mold, that is, the mold surface is long, so the infiltrant is removed by capillary action. Second, the amount of infiltration on the mold surface is smaller than that near the top of the packed bed. Thirdly, the amount of infiltration is uneven during cooling, so it takes a long time to infiltrate. Distortion may occur in the solid mold. Fourth, because the amount of infiltration on the mold surface is small, pinholes with a diameter of 5 to 100 μm remain near the mold surface, causing unevenness on the surface of plastic molded products using this mold. Furthermore, even if the mold surface is textured, the surface of the molded product will not be excellent due to pinholes. Fifth, the lower the filling layer, that is, the closer it is to the mold surface (tJ), the smaller the amount of immersion (tJ), so the reworkability when modifying the mold surface also deteriorates, and a molded product with an excellent surface cannot be obtained.

It is an object of the present invention to solve the above-mentioned problems and at the same time to provide a practically usable sintered mold and a method for manufacturing the same, in which a cooling passage can be provided along the vicinity of the mold surface.

[Means for Solving the Problem] In order to achieve the objective, the inventors of the present invention have repeatedly conducted research and development, and as a result, in manufacturing a sintered mold having cooling passages, the present inventors have developed a method of vibration-filling iron-based metal powder into the mold. In the process of sintering the iron-based powder, a first infiltrant having a shape similar to that of the cooling passage is appropriately buried in the position where the cooling passage is to be installed, and the filling layer is infiltrated in parallel with the sintering of the iron-based powder. It has been found that by doing so, it is possible to simultaneously solve the above-mentioned problems and reduce the processing cost of the cooling passage.

Therefore, we developed a sintered mold having a cooling cavity in the sintered mold material, which penetrates the mold and has an inner wall welded by infiltration with an infiltrant.

This mold is produced by the following technical means. That is, when manufacturing a sintered mold with a cooling passage, a first infiltration material having a shape similar to that of the cooling passage is buried in the position in the mold where the cooling passage is to be formed, and an iron-based After forming a packed layer by vibrating metal powder, a second layer is placed on top of the packed layer.
The mold, the iron-based metal powder, and the first and second infiltrant materials are heated to the sintering temperature of the iron-based metal powder to promote sintering and infiltration, and a cooling passage is provided. Manufacture sintered molds.

[Function] First, the iron-based metal powder used in the present invention accounts for most of the raw material powder, and specifically, depending on the required characteristics of the sintering mold, pure iron powder, low-alloy copper powder, high-alloy copper powder, etc. Alloy steel powder or alloy steel powder containing iron is used.

Their particle size may be a powder having a known particle size distribution. If necessary, elements useful for improving the mechanical properties of the sintered mold, particularly hardness and strength, such as a small amount of Ni in graphite powder or non-ferrous metal powder, may be added.

Cu or the like may be appropriately added to and mixed with the iron-based metal powder to form an alloy during sintering.

For mixing raw material ferrous metal powder, graphite powder, non-ferrous metal powder, etc., a normal ■ type mixer or double cone type mixer is used. The thus prepared powder is filled into a mold, for example a ceramic mold. The powder layer filled inside the mold increases its strength through sintering, and must have sufficient strength up to the temperature at which the shape of the mold can be transferred correctly, and must not impair the transfer of the mold due to a significant reaction with the powder. Good.

The internal shape of the mold is such that the sintered body can be used directly as a mold after sintering and infiltration, or it can function as a mold without significant processing.

The first and second infiltrant materials used in the present invention may be the same material or may be different materials. In short, the material may be any material as long as it melts at a temperature below the sintering temperature of the iron-based metal powder provided, and may be an alloy, a single metal element, or an alloy specially prepared as an infiltration material. Suitable infiltrant materials include copper, brass, tin, zinc, aluminum, Cu-3%Co alloy, Cu-Fe-Mn alloy, and the like.

The infiltration material may be a powder compact or an ingot material, and if it is a powder, it is used after being shaped into a desired shape.

The first infiltrant material may be melted into a desired shape, or may be manufactured by cutting. The first infiltration material has a round bar shape,
It may be in the shape of a square rod or a pipe (as long as it melts after infiltration and becomes a cooling passage for cooling water, etc.).The first infiltrant material may be a foil or sheet made of copper or the like that can be infiltrated. The infiltrated amount or infiltrated material is wrapped in a rod shape with a mesh having fine openings, paper or organic sheet that can be sintered in the subsequent sintering process, or the infiltrated amount is filled in an organic hose. The preferred shape of the first infiltration material is a straight round with a diameter of 7 to 20 mm, although it varies depending on the mold material, mold size, shape of the molded product, size of the molded product, etc. It may be a rod or a round rod curved to match the surface of the mold.In order to ensure the amount of infiltration as much as possible, it is preferable to bury two or more round rods per filling layer in one mold.

In the case of infiltration powder, the shape of the second infiltrant material is a disc-shaped molded body with a diameter of 60 mmφ x 50 mm, or a 100 mm shape.
Corner moldings are good. In the case of sawn lumber, block-shaped infiltration material is used. This infiltrant is used to compensate for the lack of the first infiltrant in terms of the amount of digestion material.

The raw material iron-based metal powder can be filled into the mold by a dry method or a wet method in the form of a slurry, and by applying vibration,
In the process of vibratory filling of iron-based metal powder, the first infiltrant is buried in the position where the cooling passage will be installed, additional powder is filled again, and vibration is applied. Generally, if the first infiltrant is placed so as to reach the opposite side from one side of the mold, the holes at both ends of the cooling passage can be easily found after sintering and infiltration. The water cooling cap may be welded or may be attached by cutting a thread into the mold.

The vibration method may be any method such as electromagnetic vibration or mechanical vibration. Further, by applying a pressure that is extremely lower than the pressure of the conventional pressure molding method using iron-based metal powder metallurgy during or after the vibration, the filling property can be further improved. This pressure may normally be 1 kg/cm' or less, and has the advantage that it not only improves the filling property but also improves the transferability of the edge portion of the mold.

By using this method, large molds can be formed without using the expensive presses used in normal powder metallurgy.
Since it can be packed inexpensively and easily, l
It is suitable for manufacturing plastic injection molds as large as 1 m x 1 m.

Next, the mold filled with iron-based metal powder is placed in a furnace and sintered and infiltrated. As mentioned above, the mold needs to maintain its strength up to a temperature at which the iron-based metal powder develops strength through sintering. Sintering and infiltration are performed in a reducing atmosphere, inert atmosphere, or vacuum, and after sintering, the ceramics, etc. are demolded.

If the present invention is adopted in this way, the above-mentioned first to fifth
All of the above problems are solved, and since cooling passages are provided along the mold surface, machining of cooling passages in the mold can be omitted after sintering. Note that the cooling passages are preferably arranged so that the contact surfaces of the substance to be cooled, such as resin, are evenly cooled.

Further, as another method for manufacturing the mold of the present invention, there is a method in which a through hole is provided in a sintered mold, and then an infiltrant is poured into the hole and infiltrated from the inner wall of the hole.

[Example] Average particle size 230 μm (particle size range 15
0~500 LLm) water atomized pure iron powder 48% by weight
40% by weight of water atomized pure iron powder with an average particle size of 29 LLm (particle size range 15-63 LLm) and an average particle size of 4.8 μm (
The powder was mixed with 12% by weight of carbonyl iron powder having a particle size range of 10 Iv m or less).

230 kg of this mixed powder is
When charging into a 0mm ceramic mold, first charge the powder to below the position where the cooling passage is provided, then perform vibration filling.
After reaching the position where the cooling passage is installed, the vibration is stopped and the first infiltrant material is made of a Cu-Fe-Mn alloy and has a diameter of 5 mmφ and a length of 300 mm that matches the inner surface dimensions of the mold. 4 pieces in parallel on the same plane at equal intervals (weight 1.5 kg)
Place the powder in place and vibrate fill again. After that, a second infiltrating material (weighing 73
．． 5 kg) was loaded. A total of 75 kg was used for the first and second infiltration materials. They were heated in a N2 atmosphere. The conditions were that the infiltration time was shortened by 21) r from the comparative example described later, and after heating at 1000'C for 6 hours+ to sinter the packed bed, the temperature was raised to 1130°C over 2 hours.
While promoting sintering, the first and second infiltrant materials were melted to promote infiltration. Holding time at 1130℃ is 2 hours
Then, it was cooled down in the furnace. After cooling, the infiltrated sintered mold was taken out from the mold, and the number of pin poles in the lower part of the sintered body, that is, the surface layer of the mold was examined. The results are shown in Table 1.

Table 1 Comparative Example Without using 1.5 kg of the first infiltrant shown in the example,
The sintering mold was prepared in exactly the same manner as in the example except that 75 kg of the second infiltrant material was placed on top of the packed bed instead, and the infiltration time 2)] of the example was extended to 41 + r. I made a prototype. Table 1 shows the results of examining the number of pinholes in the comparative material at the same position as the lower surface layer of the sintered mold obtained in the example.

As shown in Table 1, the number of vinyl poles was smaller in the Examples than in the Comparative Examples even though the infiltration time was short. Moreover, the amount of infiltration was large in the examples. Furthermore, when testing the infiltration properties of the mold surfaces obtained in Examples and Comparative Examples, it was found that the molds in Examples with a large amount of infiltration on the mold surface had excellent welding workability with copper-based welding rods. Understood. Further, when the end of the cooling passage opening in the example, that is, the vicinity of the opening in contact with the side surface of the mold, was polished with sandpaper and observed, it was found that the infiltrant was densely welded to the inner wall of the cooling passage. In addition, in a test in which cooling water was flown, no water was observed to flow onto the mold surface.

On the other hand, when comparing the results of this example with the experimental results of the method disclosed in Publication Patent Publication No. 57-500029 for burying stainless steel tubes, it was found that the method according to that publication resulted in holes in the vicinity of the hole just below the duplex. Many pinholes were observed, indicating insufficient infiltration, and therefore the number of pinholes on the mold surface was higher than in this example (approximately 40 pinholes/ ), Oc m x
It was 10 cm.

Further, in the method according to the publication, the cooling ability was inferior to that of this example because of the presence of the stainless steel tube and the holes.

[Effects of the Invention] According to the present invention, when the sintered mold provided with the cooling passage by the first infiltrant was used for plastic injection molding, it was suitable as shown in the above results.

Further, according to the present invention, by making the cooling passages thicker and increasing the number thereof, the infiltration time can be significantly shortened, the sintering mold surface is also improved, and the cooling capacity is also excellent.

By providing a cooling passage according to the present invention, the number of mold processing steps is reduced, and a sintered mold with excellent mold surface characteristics can be manufactured at low cost.

Claims (1)

[Scope of Claims] 1. A sintered mold, characterized in that the sintered mold material has a cooling cavity that penetrates the mold and whose inner wall is welded by infiltration with an infiltrant. 2. When manufacturing a sintered mold having a cooling passage, a first infiltration material having a shape similar to the shape of the cooling passage is buried in the position in the mold where the cooling passage is to be formed, and an iron-based infiltration material is embedded in the mold. After vibrating and filling metal powder to form a packed layer, a second infiltrant is placed on top of the packed layer, and a mold, iron-based metal powder and first
, a sintered mold characterized in that a second infiltrant material is heated to a sintering temperature of iron-based metal powder to promote sintering and infiltration to produce a sintered body mold having a cooling passage. manufacturing method.